A design agency asked Coupland Bell consultants to provide
engineering support for a new concept of vertical axis
wind turbine. Their client had a concept for turbines
where it had not been used before and had an innovative
solution to some of the engineering problems. Our
consultants task was to design the aerodynamics, predict
the power and efficiency and do the mechanical design
of the blades.
Our consultants researched the background of the aerodynamics
of vertical axis wind turbines and developed a spreadsheet
model to predict the blade loading and efficiency of a
simple prototype. Our consultants designed the blade
profile based on well-known NACA profiles. The model
then gave us the blade loads, which vary as the blades
go through stall on every rotation. Our consultants
stressed the blades and some other critical components
using finite element analysis.
Build and test
The first concept for the mechanical prototype blades
was a structural foam core with carbon fibre skin.
This proved difficult to make as a prototype, because
the external shape of the blades was critical to the performance
and carbon fibre prepreg doesn't lend itself to fine tolerance
hand layup without moulds. A successful alternative
was laminated timber finished by CNC routing.
The prototype turbine was successfully tested in a wind
tunnel and the blade performance was close to our predictions.
The client was able to use the test results to seek investment
for the production model and to develop the final blade